With the development of flat panel displays such as LCDs and PDPs, there arose a need to convert from an interlaced video format to a format used in the newer displays, i.e., progressive scanning. With interlacing, frames of a video are broken up into fields, where consecutive fields are configured to display alternating lines of a frame. One field may display only odd rows of pixels while the next field displays only even rows of pixels. When scanned at a sufficiently high frequency, sequential displaying of the fields produces what the human eye perceives as a complete image. In contrast, progressive scan is a technique in which an entire frame may be scanned without skipping any rows. Rows may be scanned sequentially until the entire frame is displayed.
Various techniques for de-interlacing have been developed. The techniques can be generally divided into two categories: intra-field and inter-field. Intra-field techniques utilize image information from within a single field. For example, one method involves line doubling, which fills in the missing lines by repeating existing field lines. Inter-field techniques utilize image information from two or more fields. Weaving, which involves adding consecutive fields together, is one example. Another example is blending, which combines consecutive fields by averaging their pixel values.
Each of the above techniques has its advantages and drawbacks. Accordingly, it is common practice to combine techniques. Motion-adaptive de-interlacing, for example, often applies intra-field techniques to field regions for which motion is detected between successive fields and inter-field techniques to static regions. Although it may be desirable to use complex techniques or combine multiple techniques, performance considerations should be balanced against cost. Factors that may be considered relate to computing resources (e.g., processing power, computation time, power consumption, etc.) and the cost of manufacturing a de-interlacing circuit. Current de-interlacing techniques tend to be focused on performance rather than efficiency. It is therefore an object of the present invention to provide for faster and less computationally expensive de-interlacing. Further, the present invention provides a low-cost alternative and performs better in static regions (e.g., improved image stability and decreased flicker) compared to existing low-cost techniques as a result of features such as accurate direction estimation and anti-flicker filtering. These and other features of the present invention are described below.